This study is based on the importance of reading comprehension but in fact the students’ ability in comprehending the reading text is low. The problem of this research can be stated as follow:
1. How is the implementation of group investigation method to improve students’ reading ability in descriptive text?
2. How is the improvement of students’ reading ability in descriptive text after being taught through using group investigation?
Its purposes are:
1. To describe the implementation of group investigation method to improve students’ reading ability in descriptive text.
2. To identify the improvement of students’ reading ability in descriptive text after being taught through using group investigation method.

To achieve the objectives of the study, the writer conducted classroom action research. This classroom action research was held at MTs Sabilul Ulum Mayong Jepara. The subject of the study was the grade VIII C. There were 42 students; 23 girls and 19 boys.
The writer carried out three steps. The first step was the pre-cycle. The second step was the action. The action consisted of two cycles. The difference between these cycles was on topic of material used. Each cycle consisted of teaching and learning process and a test. Data collection was done using observation, test and interview.
In analyzing the data, the writer used a descriptive qualitative and a simple quantitative measurement to find the result. The analysis of the data showed that there was a significant difference of the students’ achievement in the pre-cycle up to second cycle. The average of the students’ achievement in the pre-cycle was 57.73, the first cycle was 64.05 and the second cycle was 75.23.
Based on this finding, it is suggested that Group Investigation method can be used by the teachers to improve students’ ability in reading comprehension.